Controlling the flux of reactive species: a case study on thin film deposition in an aniline/argon plasma

D Sciacqua,E Von Wahl,C Pattyn,A Jagodar,E Kovacevic,T Strunskus,J Berndt,T Lecas

doi:10.1038/s41598-020-72634-y

Abstract

The plasma based synthesis of thin films is frequently used to deposit ultra-thin and pinhole-free films on a wide class of different substrates. However, the synthesis of thin films by means of low temperature plasmas is rather complex due to the great number of different species (neutrals, radicals, ions) that are potentially involved in the deposition process. This contribution deals with polymerization processes in a capacitively coupled discharge operated in a mixture of argon and aniline where the latter is a monomer, which is used for the production of plasma-polymerized polyaniline, a material belonging to the class of conductive polymers. This work will present a particular experimental approach that allows to (partially) distinguish the contribution of different species to the film growth and thus to control to a certain extent the properties of the resulting material. The control of the species flux emerging from the plasma and contributing to the film growth also sheds new light on the deposition process, in particular with respect to the role of the ion component. The analysis of the produced films has been performed by means of Fourier Transform Infrared spectroscopy (FTIR) and Near Edge X-ray Absorption Fine Structure spectroscopy (NEXAFS).

Highlights

The plasma based synthesis of thin films is frequently used to deposit ultra-thin and pinhole-free films on a wide class of different substrates
The physical, chemical and morphological properties of conductive polymers in general and polyaniline in particular strongly depend on their composition and on the synthesis method[25]
In comparison the decrease in absorbance at 2930 cm−1 (C–H stretching) is much less pronounced. These results show that, besides the growth rate, the chemical structure of the thin films is altered depending on the size of the hole

Summary

Introduction

The plasma based synthesis of thin films is frequently used to deposit ultra-thin and pinhole-free films on a wide class of different substrates. The exact composition of the species flux for a given precursor, and the properties of plasma produced thin polymer films, generally depends on a great number of possible external parameters as e.g.: process pressure, electrode distance, gas mixture ratios (noble gas component/monomer), power, pulse frequency, duty cycle or ratio input flow rate/pumping speed (residence time)[45] The aim of this contribution concerns the study of thin film deposition in an aniline/argon plasma and the possible control of the species flux, and the film properties by using a specific structured electrode later referred to as “channel electrode”. The characterization of the deposited films is done by profilometry, ellipsometry, FTIR and NEXAFS spectroscopy

Objectives

Results

Conclusion